Plasma-activation of tap water using DBD for agronomy applications: Identification and quantification of long lifetime chemical species and production/consumption mechanisms

Abstract

Cold atmospheric plasmas are weakly ionized gases that can be generated in ambient air. They produce energetic species (e.g. electrons, metastables) as well as reactive oxygen species, reactive nitrogen species, UV radiations and local electric field. Their interaction with a liquid such as tap water can hence change its chemical composition. The resulting "plasma-activated liquid" can meet many applications, including medicine and agriculture. Consequently, a complete experimental set of analytical techniques dedicated to the characterization of long lifetime chemical species has been implemented to characterize tap water treated using cold atmospheric plasma process and intended to agronomy applications. For that purpose, colorimetry and acid titrations are performed, considering acid-base equilibria, pH and temperature variations induced during plasma activation. 16 species are quantified and monitored: hydroxide and hydronium ions, ammonia and ammonium ions, orthophosphates, carbonate ions, nitrite and nitrate ions and hydrogen peroxide. The related consumption/production mechanisms are discussed. In parallel, a chemical model of electrical conductivity based on Kohlrausch's law has been developed to simulate the electrical conductivity of the plasma-activated tap water (PATW). Comparing its predictions with experimental measurements leads to a narrow fitting, hence supporting the self-sufficiency of the experimental set, I.e. the fact that all long lifetime radicals of interest present in PATW are characterized. Finally, to evaluate the potential of cold atmospheric plasmas for agriculture applications, tap water has been daily plasma-treated to irrigate lentils seeds. Then, seedlings lengths have been measured and compared with untreated tap water, showing an increase as high as 34.0% and 128.4% after 3 days and 6 days of activation respectively. The interaction mechanisms between plasma and tap water are discussed as well as their positive synergy on agronomic results.

Plasma‐activated water to improve the stress tolerance of barley

“…In the last few years, studies have been conducted on selected species to test the effect of PAW on seed germination and plant growth …”

“…Zhang et al and Judée et al have investigated the effect of different liquids activated by an atmospheric pressure He plasma jet on germination and growth of lentils. It has been shown that plasma‐activated tap water boosts both the early and late stages of growth, providing a growth rate similar to the activated liquid fertilizer.…”

“…In the last few years, studies have been conducted on selected species to test the effect of PAW on seed germination and plant growth. [33][34][35][36][37][38][39][40][41] Zhang et al [33] and Judée et al [34] have investigated the effect of different liquids activated by an atmospheric pressure He plasma jet on germination and growth of lentils. It has been shown that plasma-activated tap water boosts both the early and late stages of growth, providing a growth rate similar to the activated liquid fertilizer.…”

Direct Treatment of Liquids Using Low-Current Arc in Ambient Air for Biomedical Applications

“…Recently, treatment of liquids using various atmospheric pressure plasmas has attracted much attention owing to its wide range of possible applications, such as synthesis of nanocarbons and nanoparticles, sterilization of microorganisms, growth enhancement of plants, plasma farming, cancer therapy, and water purification [1][2][3][4][5][6][7][8][9][10][11][12][13]. Typically, low-temperature nonequilibrium atmospheric pressure plasma jets (NEAPPJs) or dielectric barrier discharges (DBDs) are used for activation of liquids by plasma [5,[12][13][14][15][16].…”

Plasma‐Driven in Situ Production of Hydrogen Peroxide for Biocatalysis

“…The plasma‐generated species as well as the UV photons stemming from the relaxation of excited species can interact with gases or liquids exposed to the plasma. One of the species generated in high amounts in plasma‐treated liquids is hydrogen peroxide (H 2 O 2 ), which can be a valuable oxidant for enzymatic conversions.…”